Researchers have found traces of a virus that lives on swine in a diarrhea vaccine produced by British GlaxoSmithKline and used widely in Vietnam.

It has not been known if the PCV-1 virus will cause disease in either animals or humans. But its DNA was found in the Rotarix oral vaccine used to protect against diarrhea and vomiting, AFP on March 24 cited the European Medicines Agency (EMA) as saying.

"The findings do not present a public health threat," said the agency in a statement.

"It is nonetheless clear that viral DNA should not be present in the vaccine and that its source is unclear."

As of March 24, the Health Ministry had not ordered a halt on the use of the vaccine, said Nguyen Thi Tuong Vi from the office of GSK in Vietnam.

GSK has sent notes about the finding to concerned authorities, Vi said.

The drugmaker said in a press release on March 23 that there's PCV-1 in meat products people eat every day and it causes no problem. The virus doesn't reproduce in the human body, it said.

GSK said PCV-1 is present in the cell stock used in the first stage of the vaccine production. It said it will try to change the cell stock as soon as it can.

Nguyen Tran Hien, head of the National Institute of Hygiene and Epidemiology, said "In principle, PCV-1 is not allowed in any kind of vaccine, though there's no scientific evidence that the virus would cause diseases in humans and pigs."

The virus is not the one that causes swine flu, Hien said.

Vietnam Drug Administration has asked the Preventive Health and Environment Department under the Health Ministry, and the National Institute of Hygiene and Epidemiology to advise on the issue.

It also requested GSK to provide information related to the vaccine and updates on the reactions of the US Food and Drug Administration (FDA) and the European Medicines Agency regarding the finding.

The European Medicines Agency said in a recent statement it would not take any action at this stage. It has instead requested the manufacturer to provide further information "as a matter of urgency."

Meanwhile, FDA has recommended its clinicians and medical officials to stop using Rotarix for a while to prevent any risks.

FDA said they would call a meeting in four or six weeks to review available documents on vaccines of the same kind in the US and to give more suggestions on their usage.

It has also asked for more technologies to identify virus in vaccines.

Health authorities in both the US and Europe said they would join officials from the World Health Organization to discuss the matter in the coming days.

Rotarix is given by mouth to children from six weeks onwards to treat the viral infection rotavirus, which causes diarrhea and vomiting.

It was approved in Vietnam in 2007 and 155,000 shots have been given since August that year. It is not part of the National Vaccination Program.

The European Union approved the vaccine in 2006, although the drug is not part of childhood vaccination programs of EU member states, the European Medicines Agency said.